DE102009022492A1 - Device for determining the properties of a medium in the form of a liquid or a soft material - Google Patents

Abstract

The invention relates to a device for determining the properties of a medium in the form of a liquid or a soft material, comprising: a) an acoustic waveguide comprising at least two opposing vanes (1, 2), one with a medium (L) defining the filling interior (5) and the filling of the interior (5) with a medium (L) each having an inner surface (11, 21) form an interface with the medium (L), b) a transmitter (3) for generating surface acoustic waves (S1) in the waveguide, c) a receiver (4) for receiving along the waveguide propagating surface acoustic waves (S2), which is coupled to an evaluation unit for determining physical properties of the medium (L) based on a signal the receiver (4) generates upon receiving the surface acoustic waves (S2), and d) a housing (G) in or on which at least the guide elements (1, 2), the transmitter (3 ) and the receiver (4) are accommodated, wherein at least one partial sound waves (S3) of the medium (L) is convertible on the respective inner surface (11, 21) and at least a part of the volume sound waves (S3) are transformed into surface acoustic waves (S1, S2 ) of the waveguide is convertible. According to the invention, the guide elements (1, 2) are formed integrally with the housing (G) accommodating the transmitter (3) and the receiver (4).

Description

The The present invention relates to a device for determining the Properties of a medium in the form of a liquid or a soft material, in particular a high-viscosity, dough-like or pasty medium, according to the generic term of claim 1.

A generic device is in the WO 2008/034878 described. It has an acoustic waveguide, which is formed by at least two opposing guide elements in the form of two plates and encloses an inner space which is filled with the medium to be measured. For filling the interior and making measurements to determine properties of the medium, the waveguide is immersed, for example, in the medium, or the medium is filled in or passed through the interior space of the waveguide.

about a transmitter will be surface acoustic waves in the Waveguide generated, wherein at least part of the energy of the acoustic Surface waves is coupled into the medium, so that a part of the energy of surface acoustic waves is converted into volume sound waves of the medium.

by virtue of the reciprocity of this coupling process between a Plate of the waveguide sensor and the medium becomes a part of itself in the medium propagating volume sound waves back into one of or both plates of the waveguide coupled back, so that surface acoustic waves are generated therein. By measuring and evaluating certain characteristics of this acoustic Surface waves, such as. B. their speed or their amplitudes, can be chemical and / or physical Properties of the medium are determined.

Basically, the volume sound waves are coupled at an angle δ with respect to a vertical reference line of a plate of the waveguide in the medium: δ = arcsin (c M / c S ).

Here, c _{M is the} sound velocity of the volume sound waves within the medium, and c _{S is} the sound velocity of the acoustic surface waves propagating along a plate of the acoustic waveguide.

In the with the WO 2008/034878 A2 As described apparatus, the (carrier) plates or guide elements of the shaft guide sensor are arranged separately from each other on a housing carrying them. The plates as guide elements of the waveguide each form a sealing cover for a cavity relative to the interior to be filled with the medium. In this cavity, a transmitter and / or a receiver for generating or receiving the surface acoustic waves are arranged and are optionally mounted directly on an outer, the cavity facing outer surface of a guide element.

These However, construction is relatively complex in the Production, since it must be ensured that the acoustic Surface wave guiding elements guide each of them Seal the associated cavity against the penetration of the medium. In addition, the design of the separately mounted Guide elements with regard to the mechanical loads occurring and for a desired long-term stability the waveguide thus formed only relatively expensive and cost-intensive to ensure.

Of the The invention is therefore based on the object, the above-mentioned disadvantages to overcome and a device for determining the properties a medium with a waveguide on.

These The object is achieved with the device of claim 1.

So is within the device according to the invention provided that the guiding elements of the acoustic waveguide, which limit an interior to be filled with the medium and each having an inner surface and an outer one Surface have, in one piece with a housing are executed in or on which the transmitter and the receiver of Device are included.

With such integration according to the invention the guiding elements of the waveguide in the housing can u. a. elaborate seals between the vanes and the housing be recessed. In addition, by the one-piece design the mechanical stability the entire device increases. Furthermore reflections from acoustic waves can be avoided and an adhesion of gas bubbles within the medium to the vanes be reduced.

As well is with the inventive device of Advantage associated with that achieved a higher measurement accuracy can be because there are several wave groups of surface acoustic waves are evaluable.

The guide elements embodied integrally with the housing according to the invention preferably do not only form an interface with the medium on it Rer inner surface but are also designed such that on each of the inner surface opposite the outer surface of the guide element in each case a transmitter and / or a receiver of the device is arranged, in particular fixed.

In In this context, it is further considered advantageous that the outer surface of a guide element each bounded a cavity of the housing, in which the Sender and / or the receiver is included. Such a Cavity may be through a material-removing manufacturing process, such as B. by turning, milling or drilling, within the initially formed from a solid material housing or of a corresponding housing section be. About a preferably relatively small and therefore easy To be sealed insertion opening can then the transmitter and / or the receiver in the interior of the cavity be insertable.

Of the said cavity or said cavities within of the housing, attached to the outer surface adjoin the guide elements are preferably with air or a another gas or a material that fills a decoupling the sound wave energy from the respective guide element in the adjacent Cavity suppressed. Instead, the cavities also be evacuated.

Also It may be the case with the molded guide elements of the waveguide act around a (injection) cast component.

In a corresponding alternative embodiment the housing is in a casting process around the to be arranged in it Transmitter and / or the receiver to be arranged around it produced. This means that when making the case for example, the transmitter and / or the receiver of the device already arranged in a cast die before the liquid casting material filled into the casting matrix for the production of the housing becomes. Such a cavity can already in the manufacture of the housing be formed around the transmitter and / or the receiver around.

Farther Among other things, it is equally possible that the transmitter and / or the recipient within a material from which the housing is made, is embedded. Below this is for example, understood that the transmitter and / or the receiver the device according to the invention in sections or completely positive fit within the housing are arranged by in the manufacture of the housing the initially liquid material for the production of Housing surrounds the transmitter and / or the receiver and then cured. This is special in a production of the housing made of plastic in one Injection molding process in a relatively simple manner possible.

In an embodiment of the invention Device, the housing has two housing sections on, in each case one of the two opposite ones Guiding integrated or integral with the associated Housing section is formed. In such housing sections in particular, it may be two housing halves act, between which the interior formed for the medium is. So is the medium to be measured between the housing sections einfüllbar or the housing or the housing sections are formed such that between the housing sections the medium to be measured flow through the waveguide can.

In a development of this embodiment, the Housing or the device according to the invention be formed such that a distance between the two housing sections from each other and / or an inclination of the two housing sections is adjustable relative to each other.

Preferably the housing is made of a metal, in particular stainless steel, or of a plastic, in particular of a polyetheretherketone (PEEK) or polyoxymethylene (POM). By a suitable choice of the material for the manufacture of the housing For example, it is readily possible, the invention Device also for the determination of chemical and / or physical Properties of an acidic or basic liquid to be determined as the medium to be measured.

There the conductive surface acoustic waves guide elements According to the invention, not separately to the housing must be mounted and sealed, the waveguide completely readily into the liquid to be measured or the medium to be measured are immersed to the between the interior of the waveguide lying to the two guide elements to fill.

Around an optionally located outside of the housing Evaluation unit for determining physical properties of the Medium at least with the receiver of the device connect, the housing has at least one cable guide on, over which a line from the inside of the case located receiver out of the housing is. Such a (data) line transmits a signal that the receiver upon receipt of the surface acoustic waves generated, to the evaluation unit.

Furthermore, it can also be provided that the receiver transmits signals to a lying outside of the housing evaluation wirelessly.

In analogously, it can be provided that a further (control) line to control the transmitter by another or the same cable management is relocated.

As well It may be the case in one or more cable guides partially taken lines to power lines to supply the transmitter or receiver with electrical Act electricity.

such Cable guides are relatively easy to seal, so that even when completely immersing the waveguide No medium in the medium to be measured via the cable guide gets into the interior of the housing.

Farther it is considered advantageous if the at least two guiding elements are made of a non-piezoelectric material.

Of Further it becomes for the functioning of the waveguide preferred that a thickness of one of the opposite Guiding elements is such that concurrent surface acoustic waves themselves both along the inner surface and along the outer surface of each Spreading guide element.

For the transmitter and / or the receiver of the invention Device, it is preferred that these a transducer, in particular a piezoelectric interdigital transducer. In particular, it may be provided that the transmitter and the receiver each by a piezoelectric transducer with interdigital electrodes are formed.

About that In addition, it can of course be provided that a Majority of transmitters and / or receivers used and received on and / or in the housing of the waveguide is.

Preferably have the guiding elements of the acoustic waveguide on which the surface acoustic waves and the volume sound waves each being transformed, opposing level Plates on or are completely formed from these. The inner surfaces of the plate are accordingly just trained or plan.

In an alternative embodiment, the Guide elements but also at least one domed inner Have surface. So can the guiding elements for example, by opposing sections be formed of a hollow cylinder or tube or such sections have, for. B. also be formed in each case in the form of a half-shell.

Further advantageous embodiment variants of the invention Device are also given by the dependent claims.

additional Advantages and features will become apparent in the description below of an embodiment become clear.

So show the

1 schematically an embodiment of a waveguide for the device according to the invention, with two opposing and mutually parallel plates as guide elements of the waveguide, which bordered a fillable with the medium to be measured interior.

In the sectional view of the 1 is an acoustic waveguide with two (carrier) plates 1 . 2 shown as guiding elements of the waveguide. The plates 1 and 2 which are opposed to each other and parallel to each other along an extension direction E of the waveguide are made of a non-piezoelectric material. The at a distance a opposite plates 1 and 2 continue to surround a (canal-shaped) interior 5 the waveguide in which a medium to be measured L can be filled or that through the interior 5 can flow through it.

A flow direction of a liquid or flowable medium L through the interior 5 is fundamentally arbitrary and is determined by the formation of inlet and outlet openings on the housing G. In the 1 could thus be a flow of the medium L z. B. along the extension direction E and / or perpendicular thereto.

The two plates 1 and 2 the waveguide of the device according to the invention are made integral with a housing G of the waveguide, both a transmitter 3 as well as a receiver 4 housed in its interior. Here is each of the plates 1 . 2 in one piece or integrally made with a housing portion G1 or G2 of the housing, which form two mutually symmetrical housing halves of the housing G in the present sectional view.

Both plates 1 . 2 each have an inner surface 11 respectively. 21 on, each one the interior 5 with the medium L faces and forms an interface with the medium L in each case. Within each housing section G1 and G2 is still an inboard, completely enclosed Sener cavity H1 or H2 formed, each having an outer surface 12 respectively. 22 the plate 1 respectively. 2 is facing. This outer surface 12 . 22 lies the inner surface 11 respectively. 21 the respective plate 1 respectively. 2 opposite and forms a side wall of the respective cavity H1 or H2.

Within the to the (first) plate 1 adjacent cavity H1 is the transmitter 3 arranged. At the transmitter 3 it is a piezoelectric transducer with interdigital electrodes on the outer surface 12 the plate 1 is attached. Preferably, the attachment of the transmitter takes place 3 by gluing, so that it is easy and quick to assemble.

The recipient 4 again, in the one to the (second) plate 2 disposed adjacent cavity H2 and is on the outer surface 22 this plate 2 attached. This is the receiver 4 in the region of a first end of the waveguide, while the transmitter 3 is arranged in the region of another, second end of the waveguide and the waveguide extends in the illustrated cross-sectional view between these two ends along the extension direction E.

About the transmitter 3 become surface acoustic waves S1 in the first plate 1 generated as soon as the sender 3 electrical (alternating) power is supplied. Part of the energy of these generated surface acoustic waves is at the interface of the inner surface 11 as volume sound wave S3 coupled into the medium L or converted into volume sound waves S3 of the medium L.

The two plates 1 . 2 are preferably made of a non-piezoelectric material and have a thickness d which is less than or equal to the wavelength of the generated surface acoustic waves. Optionally, thus indicate the surface acoustic waves that occur within the plates 1 . 2 Lamb waves (or modes in the transition region of Lamb waves and Rayleigh waves) propagate along both the inner surface 11 . 21 as well as along the outer surface 12 . 22 the respective plate 1 . 2 spread. Depending on the thickness d of the plates 1 . 2 For example, the surface acoustic waves will be substantially in the form of Lamb waves (d less than the wavelength of the surface acoustic waves) or in the form of waves from the transition region between Lamb waves and Rayleigh waves (d equal to the wavelength of the surface acoustic waves). In any case, the surface acoustic waves propagate along both surfaces 11 . 12 respectively. 21 . 22 the plate 1 respectively. 2 out.

Like in the 1 illustrates surface acoustic waves S1 so that starting from the transmitter 3 along the extension direction E of the first plate 1 , Part of the sound wave energy along the inner surface 11 the first plate 1 ongoing surface acoustic waves will be in the inside of the interior 5 located medium L coupled, so that volume sound waves S3 are generated within the medium L. In this case, a propagation direction of these coupled volume sound waves S3 is at a characteristic angle δ relative to a vertical reference line along the flat surface 11 the first plate 1 inclined.

Once the volume sound wave S3 on the inner surface 21 the opposite second plate 2 Once you have reached, part of your energy is in the second plate 2 coupled therewith so that acoustic surface waves S2 (for example in the form of Lamb waves or surface waves in the transition region) S2 are generated along the extension direction E of the second plate 2 spread. Also the surface acoustic waves S2 of the second plate 2 spread both along the inner surface 21 as well as along the outer surface 22 the second plate 2 out.

At any time at which the volume sound wave S3 on the inner surface 11 or 21 the plates 1 . 2 reached, part of their sound wave energy in the respective plate 1 . 2 coupled and surface acoustic waves S1, S2 in the respective plate 1 . 2 generated. While the intensity of the volume sound waves S3 on their zigzag-shaped propagation path (in the 1 denoted by P2), the acoustic wave energy of the surface acoustic waves S1, S2 within the plates decreases 1 . 2 by coupling in the sound wave energy of the medium L along its propagation path labeled P1.

Like in the 1 is apparent, reaches the volume sound wave S3, which at the angle δ in the medium on the inner surface 11 the first plate 1 was coupled to the receiver 4 at an interaction point I2 ''', proceeding along the zigzag propagation path P2 within the medium L, and its sound wave energy at the interaction point I2''' into the second plate 2 is coupled.

In addition, however, a portion of their sound wave energy at a plurality of further interaction points I2, I2 'and I2''in the second plate 2 coupled, so that acoustic surface waves S2 are formed or amplified here. In this way, surface acoustic waves S2 propagate along the second plate 2 over a comparatively long distance before reaching the receiver 4 to reach.

About the difference in transit times along the propagation path P1 to the receiver 4 passing surface waves S2 can by means of a receiver 4 associated evaluation unit of the device according to the invention (not shown) characteristic properties of the medium L - here a liquid - are determined. For this the receiver generates and transmits 4 one or a plurality of signals to the evaluation unit when the receiver 4 him reaching surface acoustic waves S2 detected.

So can be timed consecutively at the receiver 4 Incoming acoustic surface waves S2 or groups of surface waves S2 on the speed of sound within the medium L are inferred. Since the measured transit times of the surface acoustic waves S 2 coupled to the interaction sites I 2, I 2 ', I 2''and I 2''' are influenced by the properties of the medium L (in particular by the propagation velocity of the volume sound waves S 3 within the medium L 1 and L 2) the size of the angle δ), the physical and / or chemical properties of the medium L to be measured can be determined by the evaluation unit.

Analogously, different amplitudes of the through the receiver 4 measured acoustic surface waves S2 are used for determining physical and / or chemical properties of the medium L.

If the housing G of the device, the housing is arranged and provided that the medium to be measured L through the interior 5 flows through, can also be provided that by means of the device, a flow velocity through the interior 5 flowing through medium L can be determined. Thus, the flow rate of the medium has an influence on the transit times at the receiver 4 received surface acoustic waves S2, so that it can be deduced from the flow velocities.

In a further embodiment, the housing G has at least one transmitter 3 and a receiver 4 on, both a guide element or a plate 1 . 2 are assigned to the inner surface 11 respectively. 21 over the transmitter 3 generated surface acoustic waves S2 in volume sound waves S3 are convertible. In other words, for example, the transmitter 3 and a (possibly additional) receiver on a common guide element, for example. The first plate 1 or the second plate 2 arranged. So could an additional receiver on the outer surface 12 the first plate 1 opposite to that in the 1 shown receiver 4 the second plate 2 be arranged.

The device is now furthermore designed and set up to determine a temperature of the medium L on the basis of the surface acoustic waves S2 received by this receiver. This is possible because in particular the speed of the surface acoustic waves S2 along the guide element or the plate 1 . 2 to which the transmitter 3 is arranged (in this case, the first plate 1 ), depends substantially on the temperature of the medium L.

To the plates 1 . 2 opposite them and the transmitter 3 or the recipient 4 The receiving cavity H1 or H2 do not have to seal consuming, are the plates 1 and 2 according to the invention in one piece with the respective housing portion G1, G2 or in one piece with the housing G. In this case, the cavities H1 and H2 can be formed, for example, by a material-removing, in particular machining production method, such as, for example, turning, milling or drilling, from a solid material of the respective housing section G1, G2. Here then the transmitter 3 or the recipient 4 positioned via an insertion opening within the cavity H1 or H2. The attachment of the transmitter 3 and the recipient 4 on the outer surface 12 respectively. 22 the plate assigned to them 1 respectively. 2 is preferably done by gluing.

An insertion opening, over which the transmitter 3 or receiver 4 is inserted into the interior of the cavity H1, H2 is preferably located on an outer side of the housing G. In other words, the insertion does not open into the interior 5 in which the medium L to be measured is located or through which the medium L to be measured flows. In particular, since the medium L can be an acidic or basic liquid, it is avoided that a seal of the insertion opening (not shown) is directly exposed to the medium. A possible influence on the measurement by the waveguide shown can be safely excluded if the insertion opening is not on one of the plates 1 . 2 or their inner ( 11 . 21 ) or outer surfaces ( 12 . 22 ) and thus, for example, adjacent to the interior 5 located.

Of course, it can be provided that the waveguide shown with the housing G can be completely immersed in the medium to be measured L. However, the sealing of an insertion opening on the housing sections G1 and G2 is then still easier to implement than in the case of plates to be mounted separately on the respective housing section G1, G2 1 . 2 the case would be.

Furthermore, the insertion can serve as a cable guide, on the outside of a line to the transmitter 3 or to the recipient 4 is guided. Such a line can be provided both for the supply of said electronic components with electrical current, such a line can also be designed as a data or control line to the function of the transmitter 3 to control or transmit signals generated by the receiver to an evaluation unit located outside of the housing G.

As well can use a variety of different wires over one single common insertion opening from the respective Cavity H1, H2 led out of the housing B. be.

alternative or in addition, one or more different cable guides from the insertion opening be made in the housing G, via the line are led out of the housing G.

Furthermore, an electronic evaluation unit of the device according to the invention can also be accommodated within the housing G. The evaluation unit can thus be set up and provided in a further development, for example, for storing the signals received from the receiver 4 were transmitted, and then after the measurement, the stored and possibly evaluated signals via a provided on the housing G connector to a computer unit, such. A computer system.

In a further embodiment, the transmitter 3 and the receiver 4 already arranged prior to the formation of the housing G in an injection molding die. By appropriate design of the injection molding die, the (cast) material from which the housing G is made, in liquid form to the transmitter 3 and the receiver 4 placed around in the injection mold, so that the transmitter 3 and the receiver 4 are completely enclosed by the material of the housing G, respectively.

The cavities H1 and H2 are then for example already provided in the injection molding die as a negative mold, so that the transmitter 3 and the receiver 4 are enclosed after curing of the material of the housing G in the respective cavity H1, H2, without a subsequent sealing of the respective cavity H1, H2 would be necessary. Optionally, any lines already in the injection molding die can be arranged before the filling of the liquid material for the housing G, so that they already embedded in the manufacture of the housing G in this and out of the interior of the respective cavity H1, H2 to the outside are.

Deviating from the presentation of 1 can the transmitter 3 and the receiver 4 also be embedded within the material for the production of the housing G at least in sections.

Thus, for example, be provided within an injection molding die a receptacle or recess into which the transmitter 3 or the recipient 4 can be used, so that when filling the liquid material for the production of the housing G in the injection molding die of the transmitter 3 or the recipient 4 at least in sections directly into contact with the liquid material. The thermosetting material of the housing g thus forms a positive enclosure for the transmitter 3 and / or the recipient 4 , so that its intended position within the housing G can be ensured.

Furthermore, in order to be able to provide a cavity H1, H2 filled with air or gas within the housing G, which directly adjoins the outer surface 12 respectively. 22 the plate 1 respectively. 2 adjacent, it can be provided that the transmitter 3 or the recipient 4 is only partially surrounded in the embodiment described above by the material of the housing G or is not completely embedded in the material of the housing G. For this example, forms the outer surface 12 respectively. 22 a cup or cup-shaped receptacle into which the transmitter 3 or the recipient 4 is recorded positively.

Such a positive recording for the transmitter 3 and / or the recipient 4 can also be made by means of a material-removing method within a cavity H1, H2.

Alternatively, the transmitter 3 and / or the recipient 4 be completely enclosed by material of the housing G, so that no cavity H1, H2 is formed during manufacture of the housing G or the cavity H1, H2 at least not the transmitter 3 or the recipient 4 includes.

In any case, it remains essential that the plate 1 . 2 is made as a guide element of the acoustic waveguide integral with the respective housing portion G1, G2, so that its the interior 5 facing surfaces active surfaces 11 . 21 of the waveguide and the additional installation of seals for separately mountable plates 1 . 2 eliminated.

Notwithstanding the embodiment shown with flat plates 1 . 2 as guide elements of the waveguide, the guide elements can be provided with curved inner surfaces. Such guide elements, for example, by curved, itself opposite pipe sections are formed, so that the interior bounded by them 5 is designed substantially tubular.

In a further development of the embodiment of the 1 can also have multiple stations 3 and / or multiple recipients 4 be used within the device according to the invention. These can then be analogous to the transmitter shown 3 and the receiver shown 4 as well as be taken up analogous to the previous versions within the housing G.

In a further development of the device shown, the distance a and / or the inclination of the two housing sections G1 and G2 to each other (continuously) adjustable. Thus, the dimensions and the shape of the medium L accommodating the interior 5 be variable.

The Housing G is preferably made of metal, for example Stainless steel, or of a plastic, for example polyetheretherketone (PEEK) or polyoxyethylene (POM).

1

(First) Vane / plate

11

Inner surface

12

Outer surface

2

(Second) Vane / plate

21

Inner surface

22

Outer surface

3

transmitter

4

receiver

5

inner space

a

distance

d

thickness

e

extension direction

G

casing

G1, G2

housing section

H1, H2

cavity

I2, I2 ', I2' '

Interaction sites

L

medium

P1, P2

propagation path

S1, S2

acoustic surface wave

S3

Bulk acoustic wave

δ

angle

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - WO 2008/034878 [0002]
• - WO 2008/034878 A2 [0007]

Claims (19)

Apparatus for determining the properties of a medium in the form of a liquid or a soft material, comprising: a) an acoustic waveguide having at least two opposing conducting elements ( 1 . 2 ) comprising an interior space to be filled with a medium (L) ( 5 ) and when filling the interior ( 5 ) with a medium (L) each having an inner surface ( 11 . 21 ) form an interface with the medium (L), b) a transmitter ( 3 ) for generating surface acoustic waves (S1) in the waveguide, c) a receiver ( 4 ) for receiving along the waveguide propagating surface acoustic waves (S2), which is coupled to an evaluation unit for determining physical properties of the medium (L) based on a signal that the receiver ( 4 ) when receiving the surface acoustic waves (S2), and d) a housing (G), in or on the at least the guide elements ( 1 . 2 ), the transmitter ( 3 ) and the recipient ( 4 ), wherein at the respective inner surface ( 11 . 21 ) at least a portion of the surface acoustic waves (S1) in volume sound waves (S3) of the medium (L) is convertible and at least a part of the volume sound waves (S3) in surface acoustic waves (S1, S2) of the waveguide is convertible, characterized in that the guide elements ( 1 . 2 ) in one piece with the transmitter ( 3 ) and the recipient ( 4 ) receiving housing (G) are formed. Device according to claim 1, characterized in that on one of the inner surfaces ( 11 ; 21 ) opposite outer surface ( 12 ; 22 ) of a guiding element ( 1 ; 2 ) the transmitter ( 3 ) and / or the recipient ( 4 ) is arranged. Device according to claim 2, characterized in that the outer surface ( 12 ; 22 ) of a guiding element ( 1 ; 2 ) a cavity (H1, H2) of the housing (G) edges, in which the transmitter ( 3 ) and / or the recipient ( 4 ) is recorded. Apparatus according to claim 3, characterized in that the cavity (H1, H2) has at least one insertion opening, via which the transmitter ( 3 ) and / or the recipient ( 4 ) is insertable into the interior of the cavity (H1, H2). Device according to one of claims 3 or 4, characterized in that the cavity (H1, H2) is defined by a material erosive manufacturing process or by a casting process in the housing (G) is made. Apparatus according to claim 5, characterized in that the cavity (H1, H2) in a casting process around the transmitter to be arranged therein ( 3 ) and / or the recipient ( 4 ) is made around. Device according to one of claims 3 to 6, characterized in that the cavity (H1; H2) opposite an outer space surrounding the housing (G) sealed is. Device according to one of the preceding claims, characterized in that the transmitter ( 3 ) and / or the recipient ( 4 ) is embedded in a material from which the housing (G) is made. Device according to one of the preceding claims, characterized in that the housing (G) has two housing sections (G1, G2), each with one of the two opposing guide elements ( 1 . 2 ) having. Device according to claim 9, characterized in that a distance (a) of the two housing sections (G1, G2) from each other and / or an inclination of the two housing sections (G1, G2) is adjustable relative to each other. Device according to one of the preceding claims, characterized in that the housing (G) consists of a Metal, in particular of stainless steel, or of plastic, in particular of a polyetheretherketone (PEEK) or polyoxymethylene (POM) is. Device according to one of the preceding claims, characterized in that the housing (G) has at least one cable guide, via which a line from the transmitter ( 3 ) and / or by the recipient ( 4 ) is guided out of the housing (G). Device according to one of the preceding claims, characterized in that the at least two guide elements ( 1 . 2 ) are made of a non-piezoelectric material. Device according to one of the preceding claims, characterized in that a thickness (d) of at least one of the opposing guide elements ( 1 . 2 ) is such that concurrent surface acoustic waves (S1, S2) extend both along the inner surface ( 11 . 21 ) as well as along the outer surface ( 12 . 22 ) of the guiding element ( 1 . 2 ). Device according to one of the preceding claims, characterized in that the transmitter ( 3 ) and / or the recipient ( 4 ) a transducer, in particular a piezoelectric Interdigi talwandler, exhibit. Device according to one of the preceding claims, characterized in that the housing (G) is arranged and provided for that the medium to be measured (L) through the interior ( 5 ) flows through. Apparatus according to claim 16, characterized in that by means of the device, a flow velocity of the through the interior ( 5 ) flowing through medium (L) is determinable. Device according to one of the preceding claims, characterized in that the housing (G) at least one transmitter ( 3 ) and a receiver ( 4 ), both a guide element ( 1 ; 2 ) are assigned to the inner surface ( 11 ; 21 ) over the transmitter ( 3 ) are convertible into volume sound waves (S3), and the apparatus is designed and arranged to determine a temperature of the medium (L) from the surface acoustic waves (S2) received by this receiver. Device according to one of the preceding claims, characterized in that the guide elements as plates ( 1 . 2 ) are formed.